Pit type furnace



Aug. 9, 1949. 4 J. GUTHRIE 2,478,190

PIT-TYPE FURNACE Filed March 8, 1945 3 Sheets-Sheet 1 INVENTOR James M Guthrie fl- 9, 4 J. M- GUTHRIE 2,478,190

PIT TYPE FURNACE Filed llarch 8, 1945 3 Sheets-Sheet 2 '3 N I INVENTOR James/M. Gui/hie @Wu/M/ 1949. J. M. GUTHRIE 2,478,190

PIT TYPE FURNACE Filed March 8, 1945 3 Slieets-Sheet 3 4- INVENTOR Fly James/ll Gui/177's Patented Aug. 9, 1949 UNITED STATES PATENT DFFICE 2,478,190 V PIT TYPE FURNACE 3 James M. Giithrie, prafton, fa}, assigh'or to Loftus Engineering Corporation, the, *Pitt'sburgh, Pi, a corporation of Maryland Application March 8, 1945; Serial No. 581,623

1 ihvntioh relates to pit-type furnaces, partioiilfirly pit-type fu'rh'ae's "for hatihg or seekihg meets or steel or e her 'metei, prepa'r'atery "to for-ting, rolling or other treatment, and the lffil'ehtioh consists in certain new and useful hi1- preveihehte in the structure of such furnaces, wh reby more ffiolht and more uniform heating or ihg'ots or bthe'r articles rhay be obtained,

Ih art is familiar with a furnace known as the center-fired pit. [As its name suggests, the pit is met! centrally, through its bottom or hearth and the bu'rhing eemmher fuel streams vertically upwara b'twe'e'h the charge of meats so "rt'ed n the pit bottom around the biirher o7 hihg'. I The stream offflairies impinges against the Cover of the pit and spreads, umhreue, like, e'vr the charge, and their the flames and hot prodfiots of oorhb'ustion desoehd from the amtren in streams s'pa'ced radially outward from the burning bol'uinh 'siist'ained b9 the central turner. Upon approaching the bottom of the bit the streams of hot waste gases fihd egress through dutg'o ports, which op'eh through the pit side walls ahd coinhruh'ioate with heat-ekchan'ge means that are 'e'fiective to salvage lar'g' diiahtiti'es of residual heat from the gases and to transfer the heat to the combustion air which is fed to the burner. While many advantages have been recognized ifl the lite of the htT-fiid pit, several disadvantages are to be noted: For example, the arrangement or the burner hi the center of the pit floor results in a reduction in the ihgot oapaity of a pit orgiven size, the ca acity of a pit being iii general proportional to the area of the pit bottohi Whih is available to receive ingots. consequently, inorder to obta'ih a, specifiedpit capab'ity, it has been hecessary to biiild a larger and more oostly Tpit than weula be the case if the ehtire bottoiil of the pit were available for the support of ingots. Additionally, "it may be hoted that the ifnbihgihht of a stream of burning fuel against the 'pit eater is deleterious to the cover structure. Furthermore, wheh the buiher in 's'ervioe fails to functlbh properly, the eri'ti r'e pit must be shut do'w'ri, it being understood that it is not iifioommoh for barriers to rediiire attntioh 'oVer proiehgea periods of servic 7 In accordance wrthrny resent ihv'ehti'oh, ;I aii'h to eliminate the dbjtiohs er th center-fired bit, while (retaining its more importaht advantages, as Well as obtai'riiil'g' better distiibfitibfl of the flow of the flames and hot gases between and ever the surfaces of all of the ingots charged and supported upon the hearth of the pit, p The invention will be understood upon the ref- Claims. (01. $263 43) er hee to the accompanyi g drawings, in which:

rtrghre 1 s a agmentary view in lan of a battery of tits, affording exemplary embodiineht off the invention;

Figure 2 'i'sfa view to larger scale and in ve'rt'iea! se on (if the of the pits, the plane of sedtfori rig indidated at II-II in Figure 1;

Figure 3 is avi'eW irl 'b'i'ossseotioh through the pit, as "s'rl Oil the pl'afi'e III I1I Of Figure 2; and

Figur 4 is view on the plane IV-IV of more 2, showing fthe pit ih side elevation, and illlisti ihg a set or h'at-kbhh'g'e "uhits in verti'oaljseotioh. V

he pit 'furrfabe of te inver'itiori may be con- Sitrubtfi as "a ulfit havlh'g a single pit, 01" it may have a battery bf pits, 'ihdibated by the refereh er'al z Figure 1. The pits are advent quare Tor rectangular as viewed 1 peripheral Walls 3, 3 and 4, 4

i ternany eurv v utwaraly to increase the dura- 'b'ility arid stuldlheSs "O'f tibhstiuctioh. The Tu'rhaeestrueture is built of refractory brickwork bolfhe th "suitable eohe'rete foundations 5'; the pit pm i supported upon a platform of steel fil's 6, mm ,to's dow 0h beams 1 that rest 'upoh theffoundatiofi; arid the structure is eneesei "with stee1 plate, laterally reinforced and tied by fiiea'hs of eohventiorial steel buckstays and braces, the latter members being omitted froth the dra'wlhg-s 'for the sake of clarity of illustiatiofi. p

The health "or 'bbttbrh 8 or the pit irlolude's one 'pi'lfilore ole tit openings 9, which are norih u y filled wit t e 'coke breeze 1'0, or other suitable rhatierial provides the 11001" upon which the ihgbts ll stand, as "shown in Figure 2. The pit provided with a cover l2 that is temporarily removable to permit the ingots to be charged into the pit and removed. It will be observed that the entire area, of the bottom of the pit is available for the support of ingots, with the ingots arranged and spaced properly in ac- "coruance 'vvith ingot size and shape.

present invention relates particularly to "the origfarlizatioh of a plurality "of burners for each pit, together with an effective arr'arlh'e'ment 6f Waste gas' ports for removing the Waste gases orproduets or orhbustion from the pit, st to th end that a more effe'tlve dis- 'trib'l'ftioh of heating effect may be established and 'rhaihtaified thro'uhoutall portions of the pit ehttrhheh t ohm when the pit is fired at a mammoth hat'i'hg capacity but also when the 3 burners are turned down for soaking or holding the charge of ingots.

In its general aspects the invention constitutes certain new and useful improvements in the pit furnace disclosed in United States Letters Patent No. 2,085,811, granted July 6, 1937, to Fred H. Loftus. In the structure of this patent two burners are provided in one sideor endwall of the pit and below such burners outgo ports open through the same wall into two regenerators. Both burners are adapted to be fired con tinuously while the regenerators are alternatelyoperated, after the manner that the regenerators of an open hearth furnace are" operated," to fur-' nish preheated combustion air to the burners.

In improvement of such arrangement, I provide a burner i3 for each corner of the pit, and it is of the essence of the invention that the burners comprise long-flame luminous burnersburners which project lon columns, or jets of luminous flame transversely of the upper portion of the pit chamber and preferably above the tops of the ingots therein. It will be perceived that two of the four burners l3 are arranged in each of theopposite walls 3, 3 of the pit, with the burners in each wall spaced apart a relatively great distance peripherally of the pit. It is important to note that the burners in the opposite walls are so complementarily inset or spaced from the adjacent pit corners that the streams of flame (note arrows A, Figure 1) projected by the burners in one wall are interdigitated with respect to the streams of flame directed across the pit'by the burners in the opposite wall. One burner in one of the walls 3 projects its flame between and in substantial parallelism with the flames projected by both of the burners in the opposite wall, This arrangement of long-luminousflame burnerscontributes to the obtainment of amore perfect distribution of firing and heating'efiect 4 When opening a pit in accordance with usual practice, the firing rate of the burner or burners is reduced, and the cover is moved to one side or the other, depending upon which side of the center line of the pit it is desired to remove or to charge ingots. The cover is not removed en'- tirely from the mouth of the pit, but is moved only to the extent necessary to give the required access, since it is desirable to minimize the loss of heat always encountered when apit is opened. By virtue of the burner arrangement herein disclosed, when the pit is opened the flames of the burners provide a screening effect across the area of the opening and thereby serve to minimize the loss of heat from the pit. This effect is obtained regardless'of which side of the pit is opened.

Advantageously, all of the burners (two burners in this case) in each wall 3-are'mounted in angular position relatively to the walls 3. One of the burners in each wall 3 directs flame tangentially, or approximately so, with respect to the adjacent Wall 4; that is, theburners which in the herein illustrated structure appear at the lower right-hand corners of the pits 2 (Figure 1) and the burners which appear at the upper left hand corners, are arranged to direct their flames Thus, optimum arrangement of the outgo ports is such that the drafting of waste gases from the bottom of the pit is substantially symmetrical with respect to the firing efiect of the burners above the ports.

.While 'a single outgo port, or row of three or more ports, may be arranged in each wall 3 to give this desired effect, I advantageously provide one outgo port for each burner, with each port arranged substantially directly below the associate burner.

The effect of the described burner and outgo port organization isto insure at all rates of firing a uniform distribution of heat throughout the pit chamber and its charge. As the art well knows, a luminous flame burner is one whose flame contains unburned particles or molecules of fuel. In the travel of the jetted fuel from the burner these particles are progressively heated to incandescence and burned, so that the heat release of the flame is distributed over a long path of flame travel, rather than being concentrated at a point located a relatively short interval from the burner. Accordingly, my provision of interdigitated streams 'of long luminous flames at the tops of the ingots does not means that combustion is completed above the tops of the ingots. On the contrary, burning tongues of flame are drawn downward between the ingots as well as between theringots and the pit walls, such movement of theflames being promoted by the pressure created by the injected burning fuel and air at the top ofthe pit, plus the suction of the draft acting through the outgo ports. A beneficial prolongation and distribution of combustion, anda thoroughly disseminated movement of the hot waste gases, are provided in the pit at all firing rates.

The heat-exchange 'means I5 comprise recuperators, and I provide a set of two recuperator chambers H on each side of each pit, one recuperator chamber for each outgo port [4. Each recuperator chamber includes a bank of heat-exchange tubes l8 extending between, and opening at their opposite ends through, walls l9 and 2B. Thewaste gases streaming from each outgo port enters the top of its associate recuperator chamber, and flows downwardly between and leading to a suitable stack, or exhaust fan, which is not shown but will be understood to be of conventional construction. In this case it will be seen that the two recuperator chambers on each side of the pit discharge into a common flue 3|, and it will be also understood that the usual stack or flue dampers or valves will be provided in'the flues leading from the two sides of the pit to provide, in conjunction with conventional furnace controls, proper pressures within the pit.

'Betweenthe two recuperator chambers I! on eachside of the pit,'an air chamber is provided, and this air chamber is divided by a horizontal partition 30 into upper and lower compartments 2| and 22. Air forcombustion is introduced by a cold air inlet pipe 23 into the lower air compartment 22, whence it flows laterally in divided stream through the tubes It in' the lower half of the bank of tubes in each set of chambers l1. Tire-air; e ine'rg'irigrrqnl these lower 'tubes into header ch'eists 2'4? rises nd then news inwardly thrdugh the tubes iii the'upper half of the bank bf tubes in each chamber "IT; The air emerges mm the upper air compartment 2|, and in the course'of its flow through the recuperator structureth'e air "takes up large quantities of heat yielded bythe waste gases delivered through ports 114; The highly heatedair is delivered from coml pertinent? l to the ductsystern that supplies the fc'qmfiusnoh air to the burners l3'on the corresponding side or end of the pit. More particularly, the heated air flows from compartment 21 to a duct 2,5 that delivers into a manifold 26, and manifold 26' opens at its opposite ends into the air inlets 21 of each burner. A valve or damper 28 is provided in the manifold between the inlet duct and each burner, whereby the combustion air to each burner may be properly proportioned to the rate of fuel delivered by the fuel nozzle 28. "Conventional proportioning mechanisrri for air-fuel ratio control and temperature cohtrol'may be incorporated in the furnace structure.

Within the terms of the appended claims certain variations and modifications of the structure described may be provided or practiced without departing from the spirit of the invention.

" I'clairn as my invention:

l. In a pit-type ingot furnace of general rectangular form in plan having refractory walls, a hearth for supporting ingots on end, a movable cover, burner means for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burner means, a flue system for leading the hot products of combustion from the furnace, and heat-exchange means arranged with said flue system for preheating said combustion air; the improveh ments herein described wherein said furnace includes a combustion space between the tops of said ingots and said cover and said burner means comprise two burners opening into said combustion space through each of two opposite walls a (termed burner walls) of said furnace, the burners opening through one burner wall being offset with respect to the burners opening through the opposite burner wall, whereby the burning columns delivered by said burners are interdigitated 1 as viewed in plan, providing over the horizontal expanse of said combustion space above the ingots a turbulent body of flames and hot gases, and outlet ports opening into said flue system through the furnace walls below said burners, whereby a distributed flow of flames and hot gases is drawn downwardly from said body and caused to stream over and around the bodies of the ingots in said furnace.

2. In a pit-type ingot furnace of general rectangular form in plan having refractory walls, a hearth for supporting ingots on end, a movable cover, burner means for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burner means, a flue system for leading the hot products of combustion from the furnace, and heat-exchange means arranged with said flue system for preheating said combustion air; the improvements herein described wherein said furnace includes a combustion space between the tops of said ingots and said cover and said burner means comprise two burners opening into said combustion space through each of two opposite walls (termed burner walls) of said furnace, the

burners opening through one of said burner walls being angled toward one of the side walls interconnecting said burner walls and the burners opening through the other of said burner walls being angled toward the other side wall interconnecting said burner walls, said angled burners being offset, whereby the angled columns of burning'fuel delivered by said burners are interdigitated as viewed in plan, providing over the horizontal expanse of said combustion space above the ingots a turbulent body of flames and hot gases, and outlet ports opening into said flue system through the furnace walls below said burners, whereby a distributed flow of flames and hot gases is drawn downwardly from said body and caused to stream over and around the bodies of the ingots in said furnace.

31' In a pit-type ingot furnace of general rectangular' form in plan having refractory walls, a hearth for supporting ingots on end, a movable cover, burner means for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burner means, a flue system for leading the hot products of combustion from the furnace, and heat-eX- change means arranged with said flue system for preheating said combustion air; the improvements herein described wherein said furnace includes a combustion space between the tops of said ingots and said cover and said burner means comprise two burners opening into said combustion space through each of two opposite walls (termed burner walls) of said furnace, the burners opening through one burner wall being offset with respect to the burners opening through the opposite burner wall, whereby the burning columns delivered by said burners are interdigitated as viewed in plan, providing over the horizontal expanse of said combustion space above the ingots a turbulent body of flames and hot gases, and outlet ports opening into said flue system through said burner walls, said outlet ports being located below said burners and being arranged substantially symmetrical with respect to the burners as viewed in plan, whereby a distributed flow of flames and hot gases is drawn downwardly from said body and caused to stream over and around the bodies of the ingots in said furnace.

4. In a pit-type ingot furnace of general rectangular form in plan having refractory walls, a

hearth for supporting ingots on end, a movable cover, burner means for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burner means, a flue system for leading the hot products of combustion from the furnace, and heat-exchange means arranged with said flue system for preheating said combustion air; the improvements herein described wherein said furnace includes a combustion space between the tops of said ingots and said cover and said burner means comprise two burners Opening into said combustion space through each of two opposite walls (termed burner walls) of said furnace, the two other opposite walls (termed side walls) of said furnace being outwardly bowed as viewed in plan, the burners in said burner walls being angled relatively to said side walls, whereby the burning columns delivered by the burners in one of said burner walls are angled toward one of said outwardly bowed side walls and the columns delivered by the burners in the other of said burner walls are angled toward the other of said outwardly bowed side walls, said burning columns expanding laterally to provide a turbulent body of flames and hot gases distributed over the horizontal expanse of said combustion space above the ingots in the furnace, and outlet ports opening through the furnace walls into said flue system at points located near said hearth for effecting a distributed flow of theflames of hot gases downwardly from said combustion space and over and around the bodies of the ingots in said furnace.

5. In a pit-type ingot furnace of general rectangular form in plan having refractory walls, a hearth for supporting ingots on end, a movable cover, burner means for delivering burning columns of fuel and air into the furnace, piping for delivering fuel and combustion air to said burner means, a flue system for leading the hot products of combustion from the furnace, and heatexchange means arranged with said flue system for preheating said combustion air; the improvements herein described wherein said furnace includes a combustion space between the tops of said ingots and said cover and said burner means comprise two burners opening into said combustion space through each of two opposite walls (termed burner walls) of said furnace, the two other opposite walls (termed side walls) of said furnace being outwardly bowed as viewed in plan, the burners in said burner walls being angled relatively to said side walls, whereby the burning columns delivered by the burners in one of said burner walls are angled toward one of said out- 8 wardly bowed side walls and the columns delivered by the burners in the other of said burner walls are angled toward the other of said outwardly bowed side walls, said burning columns expanding laterally to provide a turbulent body of flames and hot gases distributed over the horizontal expanse of said combustion space above the ingots in the furnace, and outlet .ports opening into said flue system through said burner walls at points located beneath said burners and substantially symmetrical with respect to said burners as viewed in plan, whereby a distributed How of flames and hot gases is drawn downwardly from said body and caused to stream over and around the bodies of the ingots in said furnace.

JAMES M. GUTHRIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,777,125 McDermott Sept. 30, 1930 1,824,876 Culbertson Sept. 29, 1931 2,017,480 Tonnar Oct. 15, 1935 2,085,811 Loftus July 6, 1937 2,126,095 Dean Aug. 9, 1938 2,252,323 Krogh Aug. 12, 1941 2,261,904 McDermott Nov. 4, 1941 2,414,069 Snow Jan. 7, 1947 

